SCT-OS Discussion Notes Vladimir Vassiliev, UCLA

3/2 F 1/3 F Schwarzschild –type OS Aplanatic Solution (2/3, 2/3) “de-magnifying” telescope (1905)

Point Spread Function The lines show OSs with minimal astigmatism for a given value of  Preferred solution for use in ACT applications has  =2/3, q=2/3

Collecting Area and FP Curvature Light Collecting Area Focal Plane Curvature R650=2.6m dZ650=3.9 cm at 45 cm. Example for F=500 cm

OS Specifications

Vignetting and PSF Field angle [deg] Effective light collecting area [m 2 ] Field angle [deg] PSF=2MAX{  x  y } [arcmin] Vignetting at 4deg field angle: -5% PSF < 4 arcmin within 8deg FoV

Primary Segmentation Segmentation Scheme A (75 panels) Segmentation Scheme D (60 panels) 5-fold symmetry

Primary Panels Specifications

Secondary Segmentation Segmentation Scheme F (36 panels) Segmentation Scheme H (24 panels) 4-fold symmetry 8-fold symmetry

Secondary Panels Specifications

Environmental Specifications I

Environmental Specifications II The tests designed in this report have been designed to conform to ISO (International Organization for Standardization) and American Military (MIL) standards where possible, although these have been tuned where necessary to assess the suitability of mirrors for IACTs, given the permanent exposure to the environment over a period of years. Differences between the tests described here and the ISO/MIL specifications are highlighted.

FP Specifications MAPMT implementation (8x8 image pixels, 4x4 trigger pixels)

Tolerances Translational d.f. Primary displacement Secondary displacement

Tolerances Translational d.f. Focal Plane displacement FP curvature & displacement Focal Plane sag at the FoV edge is mm Delta (MAPT center to edge) – 2.9 mm Delta (SiPM trigger pixel) – 0.73 mm

Tolerances all d.f. Detailed work is in progress Error budgets, etc.

OS PBS, WBS, & ICDs Later…

Alignment Notes

Global Alignment System s Two CCDs Viewing sky and focal plane Utilize images of stars and auxiliary laser system Relative alignment of mirror surfaces Removal of low spatial frequency modes in figures of both mirrors CCD S CCD C by Phil Kaaret

Panel-to-Panel Alignment System UCLA Lab Stewart Platform 6 df of which 3 df are critical

Alignment Syetem Prototyping Prototype segment of OSS for SC telescope with Stewart Platform mounted on ALMA mirror. Assembly is made with the 5 degrees of freedom inexpensive joint design developed at UCLA Machine Shop. Individual actuators can be positioned with ~1.5  m

Actuators and angle encoders

Controller Controller board Embedded computer with OS Ethernet, wireless Ethernet, Bluetooth etc… Substantial on-board processing power available Can be aware of and apply calibration Large (or multiple) software applications possible

Gumstix Verdex XM4 Marvell (Intel) XScale PXA MHz ARM based CPU 64MB RAM 16MB Flash 60-pin Hirose I/O connector. General purpose I/O (GPIO) and alternate functions Simple Gumstix I/O expansion boards or custom board Actual size: 8cm × 2cm $ (1 unit)

Gumstix expansion boards $27.50$40.00 $25.00 $65.00 $ $99.00 Single unit prices shown

Mirror control board Stepper motor drivers ADCs for encoders and position sensors Console serial port 60-pin Hirose connector

Mirror control board w/CPU & E-net

Edge Sensors Non-imaging PSD or WebCam Number of sensors per mirror: 4-6 Provide redundancy and over- constrain system to tolerate possible failures of sensors

Mirror control software On-board software: o CORBA interface with central computer – respond to commands, store/retrieve state data in central database o Move mirrors by pulsing motor controllers o Monitor encoders during motion – guard against collision o Sample PSDs and temperature (?) as necessary o Assist in calibration of PSDs and Stewart platform Central control software: o Monitor star images (focal plane CCD) o Calculate required facet motions based on elevation and temperature, and input from CCD & PSDs if necessary o Coordinate motion of mirror facets by S. Fegan

Newspaper Ad The 9m diameter original Schwarzschild IACT is an inexpensive, high-performance telescope that is easy-to-use, maintenance-free, and completely portable. Its wide field of view, beautiful images and ease of use make it an excellent telescope for beginner and expert optical and gamma-ray astronomer alike. just a dream… (1 st AGIS Meeting, UCLA)